1. Field of the Invention
This invention relates generally to a device for interrupting a circuit in the event of unbalanced currents to and from a load, and more specifically, this invention relates to a resettable circuit interrupter that is encapsulated in a plug-in unit.
2. Description of the Prior Art
A number of situations exist in which an imbalance in current flow to a load and in the return line to the source creates hazards or undesired conditions. Circuit interrupters are employed to disconnect power from the load in the event of such hazardous or undesired conditions. Specific examples of the type of circuit interrupter utilized include the appliance leakage circuit interrupter (ALCI) and the ground fault circuit interrupter (GFCI).
Various types of ALCI's and GFCI's have been utilized in the past. Frequently, the ALCI or GFCI is included in the circuit of an electrical receptacle outlet box or in the appliance or other electrical device being plugged into the receptacle. However, when such built in devices are not utilized, it is desirable to have a protective circuit interrupter that can be plugged into the receptacle to protect any appliance or other device that is to be energized from that receptacle.
After such a circuit interrupter has been actuated, either as the result of an undesired situation, such as a ground fault current, or by a momentary line surge, it is desirable to be able to reset the device for future use. However, it is also necessary that the resetting not take place when power is being applied to the load, when a ground fault exists, as a dangerous condition could be perpetuated. Accordingly, provision has to be made for resetting such that power is not conveyed to the load during the resetting operation.
Various types of resettable circuit interrupters have been utilized in the past. A resettable device for use in undervoltage protection is illustrated in U.S. Pat. No. 4,567,456--Legatti, assigned to the same assignee as the present invention. Another example of a reset mechanism utilized in connection with a GFCI incorporated into an electrical receptacle wall box is found in U.S. Pat. No. 4,209,762--Samborski et al. Although illustrative of resettable devices, these prior art arrangements do not utilize the approach of the present invention.
In addition to the basic operational requirements, such plug-in circuit interrupters should be relatively small, simple and as low cost as possible. The resettable circuit interrupter of this invention satisfies those requirements.